Method of treating orienird polyethylene terephthalate film with an halogenated fatty acid



United States Patent METHOD OF TREATING ORIENTED POLYETHYL- ENE TEREPHTHALATE FILM WITH AN HALO- .GENATED FATTY ACID Allan Robert Andrew Beeber; Elizabeth, NJ and Daniel.

S. Spechler, Brooklyn, N.Y., assignors to Keuffel &

sser Company, Hoboken, N.J., a corporation of New ersey No Drawing. ApplicationMay 2, 1957 Serial No. 656,513

6\Claims.- (Cl. 117-118) This invention relates to. a method of pre-treating a high molecular weight oriented polyethylene terephthalate filmlto make it receptive to coatings of organic materials. In recent years polyethylene terephthalate films are-being used-more and more in the drafting and reproduction fields. For these purposes it is necessary to apply various types of organic coatings to the polyethylene terephthalate film base. For example, coatings containing an abrasive material, such .as silica, are applied in order to make the material receptive to pencil and ink. lines. The material is then used for making drawings where dimensional stability is an-importantfactor; for example, in lofting, as practiced in the aircraft industry. Since it is very often desirable to make copies of the highly dimensionally stable drawings, photosenstivecoatings have also been applied to the polyethylene terephthalate base mater-ial- The Present invention Particularly u f. produce a visible etch onthe. surface of the film which may be undesirable in some cases although not in others.

as a pre-treatment forpolyethylene terephthalate base material to which it is'desired to apply these various PhD? tosensitive or drafting surfaces.

Polyethylene terephthalate film is characterized by a hydrophobic chemically inert surface. As a result of the hydrophobic nature and chemical inertness of this surface,-it is very diflicult to form an adhesive bond between any organic coatingv and the polyethylene terephthalate film. Various techniques have been tried to improve the adhesionbetween this type of base material and various organic-coatings.

Theseinclude 'abrading the surface in order to roughen it and treating the surface with chemical reagents in order to etch the surface. Now a treatment has been found which makes the surface receptive to a wide variety of organic coating materials. without producing a visible etch on the film base. The pre-treatment of the present invention greatly improvesthe adhesion of a Wide variety of organic resin materials, includingvinyls, acrylics, cellulosics, styrene, polyethylene, alkyd resins, epoxy resins, electromers, etc.

According to the present invention, the polyethylene terephthalate film is coated witha solution of a halogenated fatty acid in an organic solvent and then the coated film is heated to a temperature in the range from 100 F. to 300 F. to remove the organic solvent, to react the halogenated fatty acid with the surface of the polyethylene terephthalate film, and to remove the excess halogenated fatty acid by evaporating it from the surface. Suitable halogenated fatty acids for the purposes. of the present invention include chloracetic acid, dichloroacetic acid, trichloroacetic acid, trifluoroacetic acid, chloropropionic acid, perfluorocaprylic acid and similar halogenated fatty acids. These halogenated fatty acids may be dissolved in any inert solvent with which they are compatible. Suitable solvents include the hydrocarbons, particularly the aromatic hydrocarbons, alcohols, esters, such as ethyl acetate, halogenated hydrocarbons such as carbon tetrachloride, etc. However, aqueous solutions of the halogenated fatty acids do not work satisfactorily because such solutions do not wet the sur- 2,893,896 -Paten'ted1 J uly- 7,

2 faceof the polyethylene terephthalate filmevenly. When treating polyethylene terephthalate'filins according to the present invention, it .is .not necessary to neutralize the acid used by treatingthe. surface with an alkaline material.

7 Example 1..

A solution is made by dissolving 1.5 lbs. of trichloroacetic acid in33.6 lbs. o'f'toluo'l; This solution should be prepared in-a -glass oi. stainless. steel container.

This solution is coatedontb' the surface 'o'fa-polyethy lene terephthalate film, for'example, by means of 'a roller which is partly-immersedin the solution-and 'transfers the solution to the surface of the film. 'I-he film then passes into alieating chamber-held at a-f-temperature-of about250 F. which drives ofi thjesolvent and reacts the trichloroacetic acid withthe surface of 'the film. I The excess trichlor oaeetic acid is also driven ofi.

After being subjected-to this-treatment th'e film' may be coated with-any of the-coatings disclosedinco-pending application, Serial #496,602;- fild' March 24, 1 955, by Allan R. A. Beeber and Daniel S; Spechler. The adhesion of all of these coatings-.--will be greatly improved because o-fthe ,pre-treatment with .trichloroacetic acid. Depending upon the ex'actresults"souglit, it is pos'sibl'e to vary the conditions described aboveover. a considerable range. For example, the concentration of the trichloroe acetic acid in'the coating 'solu'tion'may range from about .2% up to thesaturatio'nconcentration ofthe 'trichloroacetic acid in the particular solvent'used. However, the higher concentrations of tri'chloro'acetic acid'will tend to If it is desired that the-final product be completely transparentfa'visible etch should, ofcourse, be avoided. On the other-bandit the'final' product ist'o be provided with a pencilisurface, as by coatingv itwith an organic coating, including silica, the presence of'a visible etch may not be objectionable. In most cases it has been found desirable to avoid visible etching of the film since perfectly satisfactoryadhesion: of most coatings can be obtained without any visible etching.

The temperatureat which the film is heated can also be varied over a wide-rangefrom about 1.00. F. to 300 F. It is not desirable to go. above 300 F. because beyond this temperature polyethylene-terephthalate films becomeaffected.- At these higher temperatures the films tend to shrink. Ibis-possible to improve the adhesion of some coatings by treatingfithesurface of the polyethylene terephthalate film with the halogenated fatty acid atroom temperature. However inmost cases it is preferred to use elevated, temperatures. Ihetemper'ature used will depend to some extent upon the concentration of the acid in the solution. Treatment. with weaker solutions at a higher temperature. may give thesame effect as treatment with stronger solutions at a lower temperature. The length of time-that the solution remains on thesurface of the polyethylene terephthalate film will also affect the result which is obtained. Thiswill depend upon the construction of the particularcoating machine used and some of the otherfactors; such as the, concentration of acid, and the temperature. at which it is applied may have. to be adjusted accordingly;

Example 2 A polyethylene terephthalate film pre-treated according to Example 1 was coated with a solution made up according to the following formula:

10 lbs. of pigment (Si0 5 lbs. of alkyd resin-solids 5 lbs. of nitrocellulose solids 1 oz. of cobalt naphthanate containing 6% cobalt (drier) 40 lbs. of solvents (selected from suitable esters, ketones and the like, such as ethyl acetate, butyl acetate and methylethyl ketone) The finished material was provided with a surface suitable for' drafting. Highly dimensionally stable drafting materials of this typejare useful where it is desired to make a full scale drawings of apart to be cut out of sheet metal. The drawing can then be applied to the sheet metal and copied thereonby photographic means so that a template is made directly on the metal.

Example 3 A sheet of polyethylene terephthalatewhich had been pretreatedaccording to Example ;1 was coated with a filmv of nitrocelluloselacquer. A conventional photographic gelatin subbing was applied over the nitrocellulose film and then a conventional silver halide type of photographic emulsion was cast on this subbing. This produced an excellent photographic material of high dimensional stability which could be used to reproduce drawings made on the material described in Example 2. The photographic emulsion had excellent adhesion to the polyethylene terephthalate film base and could not be removed by means of cellulose Scotch tape, or by severe flexing of the film.

Example 4 Example 5 A solution containing 5% dichloroacetic acid in toluene is flowed over the surface of a polyethylene terephthalate film and drained oif. The'film is then dried in an oven at 200 F. and coated with a lacquer; The adhesion of the lacquer is greately improved over what it would be without pre-treatment with dichloroacetic acid.

Example 6 A hot solution containing 50% of chloroacetic acid in toluene is flowed over the surface of a polyethylene terephthalate film. The excess solution was allowed to drain off and the film-was dried by heating it in an oven fatty acid in said solution being in the range from .2% to a completely saturated solution, and heating said coated fihn to a temperature. in the range from 100 F. to 300 F. to remove said organic solvent, react said halogenated fatty acid with the surface of said polyethylene terephthalate film and remove the excess halogenated fatty acid.

3. The method of pre-treating a high molecular weight oriented polyethylene terephthalate film to make it reat 200 F. Lacquer coated on the pre-treated film 7 ceptive to coatings of organic materials comprising the steps of coating said film with a solution of an halogenated fatty acid in an inert organic solvent compatible therewith which wets the surface of said polyethylene terephthalate film, the concentration'of said halogenated fatty acid in said solution being in the range from 0.2% to a completely saturated solution.

2. The method of pre-treating a high molecular weight oriented polyethylene terephthalate film to make it receptive to coatings of organic materials comprising the steps of coating said film with a solution of a halogenated fatty acid, in an inert organic solvent compatible therewith which wets the surface of said polyethylene terephthalate film the concentration of said halogenated ceptive to coatings of organic materials comprising the steps of coating said film with a solution of an halogenated fatty acid in an inert organic solvent compatible therewith, which wets the-surface of said polyethylene terephthalate film the concentration of said halogenated fatty acid in said solution being selected at an effective concentration which will not produce visible etching of said polyethylene terephthalate film under the particular process conditions employed, and heating said coated film to a temperature in the range from F. to 300 F. to remove said organic solvent, react said halogenated fatty acid with the surface of said polyethylene terephthalate film and remove the excess halogenated fatty acid.

4. The method of pro-treating a high molecular weight oriented polyethylene terephthalate film to make it receptive to coatings of organic materials comprising the steps of coating said film with a solution of trichloracetic acid in an inert organic solvent, compatible therewith, which wets the surface of said polyethylene terephthalate film the concentration of the trichloracetic acid in said solution falling in the range from .2% to a completely saturated solution, and heating said film to a temperature in the range from 100 F. to 300 F. to remove said organic solvent, react said trichloracetic acid with the surface of said polyethylene terephthalate film and remove the excess trichloracetic acid.

5. The method of pre-treating a high molecular weight oriented polyethylene terephthalate film to make it receptive to coatings of organic materials comprising the steps of coating said film with a solution of trichloracetic acid in an inert organic solvent compatible therewith which wets the surface of said polyethylene terephthalate film, the concentration of the trichloracetic acid in said solution being selected at an elfective concentration which will not produce visible etching of said polyethylene terephthalate film under the particular process conditions employed, and heating said coated film to a, temperature in the range from 100 F. to 300 F. to remove said organic solvent, react said trichloracetic acid with the surface of said polyethylene terephthalate film and remove the excess trichloracetic acid.

6; The method of pre-treating a high molecular weight oriented polyethylene terephthalate film to make it receptive to coatings of organic materials comprising the steps of coating said film with an approximately 5% solution of trichloracetic acid in an inert organic solvent, compatible therewith, which wets the surface of said polyethylene terephthalatesfilm and heating said coated film to a temperature in the range from 100 F. to 300 F. to remove said organic solvent, react said trichloracetic acid with the surface of said polyethylene terephthalate film and remove the excess trichloraceticacid.

References Cited in the file of this patent UNITED STATES PATENTS 

1. THE METHOD OF PRE-TREATING A HIGH MOLECULAR WEIGHT ORIENTED POLYETHYLENE TEREPHTHALATE FILM TO MAKE IT RECEPTIVE TO COATINGS OF ORGANIC MATERIALS COMPRISING THE STEPS OF COATING SAID FILM WITH A SOLUTION OF AN HALOGENATED FATTY ACID IN AN INERT ORGANIC SOLVENT COMPATIBLE THEREWITH WHICH WETS THE SURFACE OF SAID POLYETHYLENE TEREPHTHALATE FILM, THE CONCENTRATION OF SAID HALOGENATED FATTY ACID IN SAID SOLUTION BEING IN THE RANGE FROM 0.2% TO A COMPLETELY SATURATED SOLUTION. 